QUICKSORT$($A$,$ p$,$ r$)$

if p $<$ r

then q $$ PARTITION$($A$,$ p$,$ r$)$

QUICKSORT$($A$,$ p$,$ q $1)$

QUICKSORT$($A$,$ q $+1,$ r$)$

where the PARTITION procedure is as follows:

PARTITION$($A$,$ p$,$ r$)$

x $$ A$[$r$]$

i $$ p $1$

for j $$ p to r $1$

do if A$[$j$]<=$ x

then i $$ i $+1$

exchange A$[$i$]$ A$[$j$]$

exchange A$[$i $+1]$ A$[$r$]$

return i $+1$